1. Field of the Invention
This invention relates to a device for a shape control (crown and flatness control) of a continuous rolling mill, and in particular to a device for determining a setting value of a shape operating amount (rolling force, rolling reduction, etc.).
2. Description of the Prior Art
In continuous rolling mills, it is important to keep the flatness (percentage deviation of plate from being perfectly flat) between stands or passes within an allowable range and to make the flatness as low as possible not only in order to assure product target values of the crown and flatness but also to assure proper passage of the material through the stand or stands. In order to make such shape control effective from a head end of a material, it is necessary to preset a shape control operating amount to an optimum value. In recent years, rolling mills having various shape controlling means have been proposed and placed into practice, but it is not easy to automatically preset a shape control operating amount. Commonly, settings using a predetermined table of values and settings by an operator are employed in most cases, but these settings cannot easily deal with fluctuations of rolling conditions.
An example of attempts of automation is disclosed in "Optimum Setting Controlling Method in Hot Strip Finished Rolling - Crown/Flatness Control Setting -" in The Proceeding of the 1984 Japanese Spring Conference for Technology of Plasticity. This method uses boundary maximum crowns and boundary minimum crowns which can be realized independently at individual stands under an allowable flatness range and an allowable shape operating amount range. Maximum and minimum crowns, from which a product target crown and a product target flatness can be attained, are calculated from each individual stand. Shape operating amounts are determined based on target crowns at the individual stands provided by mean values of such maximum and minimum crowns.
According to this method, the maximum and minimum crowns are calculated while the incoming crown C.sub.o and flatness f.sub.o at the first stand and the outgoing product target crown C.sub.n * and product target flatness f.sub.n * at the ultimate stand are restricted, and hence calculations therefor necessitate complicated correcting calculations. The maximum and minimum crowns according to such calculations are converted into crown ratios which are illustrated by dotted lines 17 in FIG. 3 where C.sub.o =0 .mu.m, f.sub.o =0%, C.sub.n *=50 .mu.m, and f.sub.n *=0% (n=6).